Community-acquired pneumonia during the first post-pandemic influenza season: a prospective, multicentre cohort study

J Infect. 2013 Sep;67(3):185-93. doi: 10.1016/j.jinf.2013.05.006. Epub 2013 Jun 6.


Objectives: To determine the aetiology, clinical features and prognosis of CAP during the first post-pandemic influenza season. We also assessed the factors associated with severe disease and tested the ability of a scoring system for identifying influenza A (H1N1)pdm09-related pneumonia.

Methods: Prospective cohort study carried out at 10 tertiary hospitals of Spain. All adults hospitalised with CAP from December 01, 2010 to March 31, 2011 were analysed.

Results: A total of 747 adults with CAP required hospitalisation. The aetiology was determined in 315 (42.2%) patients, in whom 154 (21.9%) were due to bacteria, 125 (16.7%) were due to viruses and 36 (4.8%) were mixed (due to viruses and bacteria). The most frequently isolated bacteria were Streptococccus pneumoniae. Among patients with viral pneumonia, the most common organism identified were influenza A (H1N1)pdm09. Independent factors associated with severe disease were impaired consciousness, septic shock, tachypnea, hyponatremia, hypoxemia, influenza B, and influenza A (H1N1)pdm09. The scoring system evaluated did not differentiate reliably between patients with influenza A (H1N1)pdm09-related pneumonia and those with other aetiologies.

Conclusions: The frequency of bacterial and viral pneumonia during the first post-pandemic influenza season was similar. The main identified virus was influenza A (H1N1)pdm09, which was associated with severe disease. Although certain presenting clinical features may allow recognition of influenza A (H1N1)pdm09-related pneumonia, it is difficult to express them in a reliable scoring system.

Keywords: Clinical features; Community-acquired pneumonia; Influenza A (H1N1)pdm09; Mortality; Post-pandemic period.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Bronchoalveolar Lavage Fluid / microbiology
  • Bronchoalveolar Lavage Fluid / virology
  • Community-Acquired Infections / epidemiology*
  • Community-Acquired Infections / microbiology
  • Community-Acquired Infections / virology
  • Female
  • Humans
  • Influenza A Virus, H1N1 Subtype / isolation & purification*
  • Influenza, Human / epidemiology*
  • Influenza, Human / microbiology
  • Influenza, Human / virology
  • Male
  • Middle Aged
  • Multivariate Analysis
  • Nasopharynx / microbiology
  • Nasopharynx / virology
  • Pneumonia / epidemiology*
  • Pneumonia / microbiology
  • Pneumonia / virology
  • Prospective Studies
  • ROC Curve
  • Risk Factors
  • Spain / epidemiology
  • Tertiary Care Centers / statistics & numerical data
  • Treatment Outcome